Cellulose derivative compositions



Patented Feb. 24, 1942 UNITED STATES PATENT 1 OFFICE CELLULOSE DERIVATIVE COMPOSITIONS Byron M. Vanderbilt, Roselle Park, N. J assignor to Commercial Solvents Corporation, Terre Haute, Ind., a corporation of Maryland No Drawing.

Application May 29, 1939,

Serial No. 276,421

5 Claims. (Cl. 106-181) My invention relates to cellulosic compositions which contain esters of phthalic acid. More particularly, it relates to cellulose ester compositons having incorporated therein phthalates of nitroalcoh'ols.

Cellulose esters and ethers such as nitrocellulose, cellulose acetate, ethyl cellulose, and the like, which are commonly used in the production of lacquers, plastics, and photographic films, have a tendency to become brittle in the absencse of a suitable plasticizer or'softener, and if subjected to slight flexure or torsion, are inclined to chip and crack. In order to overcome this defect, and to produce cellulosic compositions possessing permanent flexibility, the incorporation of a plasticizer has been common practice, and numerous materials have been suggested for this purpose.

Materials which are in general satisfactory plasticizers must be relatively high boiling compounds, and must be capable of imparting extensibility and flexibility to the material which is to be plasticized. Also, the plasticizer should be capable of forming a homogeneous mass when in combination with the cellulose derivative, and

the resulting product should be both water resistant and heat resistant. For use in molded plastics, and especially for injection molding, the plastlcizer should have the property of promoting flow atgelevated temperatures as well asimpart ing flexibility at atmospheric temperatures.

radical and R is chosen from the group consisting of aliphatic hydocarbon radicals and aliphatic nitrohydrocarbon radicals. Among these compounds I prefer to employ those ofthe following structural formula:

, in which R is chosen from the group consisting of hydrogen and alkyl, R and R are chosen from the group consisting of hydrogen, alkyl and cycloalkyl, and R is chosen from the group con- .sisting of alkyl and cycloalkyh In general, I

prefer to employ compounds in which both of the radicals R and R. in the first formula given above contain less than six carbon atoms, but it is to be understood that the compounds of higher molecular weight are "also useful in cellulose derivative compositions.

'Plasticizers which have this flow-promoting propertly at elevated temperatures without unduly softening the plastic at atmospheric temperatures, are often referred to as hardening agents. v

I have now discovered that cellulose derivatives, e. g.,' the cellulose esters and ethers of plastic and coating composition grades, and in particular, nitrocellulose, cellulose acetate, cellulose acetopropriate, cellulose acetobutyrate, and

ethylcellulose may be satisfactorily plasticized by means of nitroalcohol esters of phthalic acid having the following structural formula:

in which R is an aliphatic nitrohydrocarbon As examples of nitroalcohol esters of phthalic acid included in my invention may be mentioned 2-nitroethyl phthalate, methyl phthalate, ethyl 2-nitroethyl phthalate, butyl 2- 2-nitroethyl nitroethyl phthalate, cyclohexyl Z-nitrbethyl phthalate, 2-nitropropyl phthalate, methyl,2- nltropropyl phthalate, ethyl Z-nitroprop-yl phthalate, butyl 2-nitropropyl phthalate, 2--

catalyst, after which the mixture is allowed to stand for 24-72 hours at a temperature not substantially above C. The acid phthalate obtained thereby may be separated from the unreas, for example, by means of a selective solvent for the nitroalcohol. The resulting acid phthalate may then be reacted in an acid solution with an aliphatic alcohol, which is present in excess throughout the reaction. The above procedure I ing when exposed to temperatures as low as -22' C. for relatively long periods of time, and such compositions do not exhibit a tendency to discolor upon aging at room temperature, for several weeks. My new plasticizersare advantageous in the low water absorption of plastics containing these esters, being superior in this respect to commonly used plasticizers such as methylphthalyl ethyl glycolate and dimethyl phthalate.

My new plasticizers are particularly suitable for increasing the degree of fluidity of cellulose acetate compositions at elevated temperatures. This property is especially desirable in the manufacture of cellulose acetate plastics by means of injection molding, in which case the plasticizer employed should be capable of converting the cellulose acetate into a sulficiently fluid mass at molding temperatures to permit a rapid shaping of the material. The phthalates included by the above generic formula which are solids at ordinary temperatures have been found to be particularly usefulin that they tend to produce harder plastics than the plasticizers *which have been commonly incorporated into such compositions in the past. These solid esters are sufficiently good solvents at elevated temperatures to impart very satisfactory flow properties to such cellulose ester compositions without, at the same time, unduly softening the plastic at atmospheric temperature. These esters therefore constitute very satisfactory hardening agents. The use of a plasticizer possessing these properties is particularly advantageous, since it greatly aids in the production of molded products having sharp definition, and, at the same time, a hard surface, resistant to scratching and marring.

In the preparation of lacquers, films, molding powders, etc., my plasticizers may be employed singly, in combination with one another, or in combination with one or more of the plasticizers previously used in such compositions. The quantlty of ester employed will be determined chiefly by the desired characteristics of the product to be produced, and also upon the conditions to which the product will subsequently be subjected. For most purposes the phthalates may suitably be employed in amounts of approximately 20 to 70 per cent of the weight of the cellulose derivative, but I generally prefer to add such compounds in amounts of from to per cent of the weight of cellulose derivative.

In the case of cellulose derivative lacquers prepared with my new plasticizers, various solvents, diluents, pigments, and the like, may be employed in accordance with prior practices. The solvent mixture may vary widely in composition, and may comprise any of the usual combinations of solvents, latent solvents, and diluents. In formulating the solvent mixture, the usual precautions should, of course, be taken to ensure 2,274,568 acted nitroalcohol by a suitable procedure, such the presence of suflicient active solvent to prevent precipitation of the film-forming material at an undesirable stage in the evaporation of the solvent mixture.

Cellulose ester plastic compositions may be plasticized by incorporating the mixed phthalate in any suitable manner. For example the plasticizer may be added to a mixture of the cellulose ester and a solvent whose solvent power is insufllcient to produce objectionable adhesive properties in such compositions. Methyl ethyl ketone or a 50-50 mixture of ethyl alcohol and acetone have been found to be solvents of this nature which are particularly suitable for cellulose acetate plastics. Pigments or dyes may also be added, if preferred. The mass of dough-like consistency, resulting from mixing the cellulose ester with the plasticizer solvent, may be sheeted out on heated rollers, and the solvent removed by evaporation or other convenient means. The sheets of plastic, thus obtained, may-then be comminuted to give a product which is suitable for the production of molded plastics.

My invention may be further illustrated by the following specific examples:

Example I A mixture of dough-like consistency was prepared by mixing in a dough mixer parts by weight of cellulose acetate (combined acetic acid 52.9%; viscosity, 20% A. S. T. M., 52 sec.), 30 parts by weight of methyl ethyl ketone, 35 parts by 4 weight of butyl 2-methyl-2-nitropropyl phthalate. mixed, was run through extrusion rolls to form thin sheets. The solvent was then allowed to partially evaporate and the sheets resulting therefrom were broken into fine particles, and further dried for 12 hours in a well-ventilated oven at 65 0., giving a product suitable for use in the preparation of molded articles of any desired form.

Example [I A mixture of dough-like consistency was prepared by mixing in a dough mixer lbO parts by weight of cellulose acetate (combined acetic acid 55.25%; viscosity, 20% A. S. '1'. M., 40 sec.), 40 parts by weight of a solution consisting of a all-o0 mixture of acetone and ethylalcohol, 40 parts by weight of methyl Z-methyl-Z-nitropropyl phthalate, and 20 parts by weight of dimethyl phthalate. The resulting mass, when thoroughly mlxecl, was run through extrusion rolls to form tllin sheets. The solvent was then allowed to evaporate, and the sheets resulting therefrom were ground into nne particles, giving a. product suitable for the preparation of molded plastics.

Example 111 A mixture of dough-like consistency was prepared by mixing in a dough mixer 1.50 parts by weight of cellulose acetate (combined acetic acid 5thi7o; vlscos1ty,'2u% A. S; '1, M., 52 sec.), 30 parts by weight of z-nitro-z-methyl propyl phthalate, 60 parts by weight of methyl phthalylethyl glycolate and 40 parts by weight of methanol. After thorough mixing the mass was sheeted out on rolls, the solvent allowed to evaporate, and the resulting dried material ground into a powder su1table for molding purposes.

Lacquers capable of forming tough, flexible films can be prepared in accordance with my. in

The resulting mass, when thoroughly My invention now having been described, what Iclaim is:

1. A composition of matter comprising avcellulose derivative selected from the group consisting of cellulose estersand ethers, and from 25%- 50% by weight of a phthalic acid ester based on the weight of said cellulose derivative, said phthalic acid ester having the following structural formula:

in which R is chosen from the group consisting of hydrogen and alkyl, and R" and R' are chosen from the group consisting of hydrogen, alkyl and cycloalkyl, and R is chosen from the group consisting of alkyl and cycloalkyl.

2. A composition of matter comprising a cellulose derivative selected from the group consisting of cellulose esters and ethers, and from 25%- 50% by weight of a phthalic acid ester based on the weight of said cellulose derivative, said phthalic acid ester having the following structural I formula:

g R! RI! f C. O ('J l m I![ NC: O0R

vention and may be illustrated by the following specific examples:

Example IV j Grams per Solids 100 c c. of

solvents Cellulose acetate (54-55% combined acetic acid; viscosity, 20% A. S. T. M., 2-8 see.) .t 15 Dimcthyl phthalate 2 Methyl 2-methyl-2-nitropropyl phthalate- 3 1 Percent by Volatiles volume Acetone Methyl lactate 10 Ethyl acetate 30 Absolute ethyl alcohol 20 Example V Grams per Solids 100 cc. of v solvents I Nitrocellulose secondj 10 Ester gum. l0 Methyl 2-methyl-2-nitrobutyl phthalate 5 Percent by Volatiles volume Butyl acetate A 20 i0 10 10 Although the above specific examples refer to nitrocellulose and cellulose acetate compositions, it is to be understood that I do not limit the scope of my invention to compositions of this nature, since my plasticizers are useful with any of'the other cellulose derivatives, e. g., the cellulose esters and others of plastic and coating composition invention.

in which R is chosen from the group consisting .of hydrogen and an alkyl radical containing less for said cellulose acetate.

methyl-2-nitropropyl phthalate as a plasticizer for said cellulose acetate. 1

BYRON M; VANDERBILT. 

